1. Project Title: Underwater Fish Reef Creation Project within
Ashbridge's Bay Park,
City of Toronto
2. Contact
Jennifer Vincent
Metropolitan Toronto and Region Conservation Authority
5 Shoreham Drive, Downsview, Ontario M3N 1S4
Tel.: (416) 661-6600 ext. 349; FAX: (416) 661-6898
3. Agencies Involved
Metro Toronto and Region Remedial Action Plan
Environment Canada's Great Lakes Cleanup Fund
Ministry of Environment and Energy
Ministry of Natural Resources, Maple District
Municipality of Metropolitan Toronto
4. Restoration Goal
To establish structural fish habitat, improve conditions for the resident fish community, and enhance technical knowledge associated with the creation of fish habitat.
5. Project Type
Creation of new fish habitat.
6. Background and Rationale
The nearshore substrates of the Metro Toronto waterfront area are essentially uniform, consisting mainly of sand, bedrock and fine materials. Habitat rehabilitation through the creation of nearshore reef structures offers interstitial refuge and vertical relief, as well as important structural habitat for waterfront fish communities. Located nearshore, habitat structures also offer increased urban angling and education opportunities.
Fisheries surveys between 1989 and 1992 identified 29 fish species within Ashbridge's Bay boat basin. The lack of physical structure, coupled with water quality concerns at this site, may be limiting fish production. An increase in the diversity of structural habitat is expected to benefit fish communities at this location.
An underwater fish reef was construction within the Ashbridge's
Bay boat basin December
3-9, 1992.
7. Regulatory Considerations
A number of approvals from Federal, Provincial, and Municipal agencies were obtained to meet legislative requirements before conducting this project. The following outlines each Federal, Provincial, and Municipal agency involved in the approval process.
Federal
Environment Canada
Summaries of Initial Assessment as per Federal Environmental Assessment Review Process
Department of Fisheries and Oceans
Fisheries Act
Canadian Coast Guard
Navigable Waters Protection Act
Provincial
Ontario Ministry of Environment and Energy
Provincial Environmental Assessment Act (Ont. Reg. 205 8(2)(h), due to the project being a "Fish and Wildlife project")
Ontario Ministry of Natural Resources
Fisheries Act
Lakes and Rivers Improvement Act
Public Lands Act
Municipal
Toronto Harbour Commission
approval contingent upon THC receiving copies of finished work plans submitted to the Coast Guard.
Metro Parks and Property
Waterfront Agreement, 1972
Metropolitan Toronto and Region Conservation Authority
internal development project approval
8. Criteria
Danehy et al. (1991) noted that the growth rate of yellow perch and white perch (Morone americana) was greater for individuals captured over cobble/rubble shoals versus sandy sites. These authors indicated that the amount of available cover may influence growth rate based on energy expenditure differences for fish inhabiting different substrate types. The artificial reef structure was placed in an area of virtually featureless substrate to enhance fish productivity in nearshore waters.
MTRCA/OMNR summer electrofishing data shows a trend whereby a greater number of fish species are captured within sheltered boat basins having a diversity of habitats than exposed coastal location. The temperatures within these boat basin generally is 5_C warmer than outside. These findings are consistent with Portt and King (1991) who suggested that increased species richness might be attributable to environments with greater substrate diversity accompanied by appropriate water temperatures.
9. Project Design
The Ashbridge's Bay underwater fish reef was designed to provide
structural relief and spatial diversity within a relatively featureless
basin (Figure 1). The reef was constructed in an irregular outline,
centered on the 3 transects (Figure 1), conformed to the contours
of the basin and maximized interstitial spacing and edge. Ecologically
inert materials (natural aggregates) were selected.
The reef was designed to maximize:
vertical relief
irregular shape
diversity of substrates
interstitial spacing
The reef measures approximately 23.5 m from shore and is 30 m in length along the shoreline. It measures 2 - 2.5 m in height at the outside edge. The highest point of the reef is 1.0 m below datum.
10. Implementation
The project was completed between the 3rd and 9th of December, 1992. Advance planning and approvals took approximately six months. The substrate added was clean, silt-free stone. Aggregate materials were ordered 24 h in advance, with consideration being given to weather conditions (ie: rain/snow and temperature as it relates to ground conditions), progress in implementation at the construction site, numbers of trucks available for delivery by construction companies, and heavy equipment availability. Reef materials were transported to the site by triaxle/tandem trucks. Four rip-rap trucks with steel lined boxes were required. Trailers were not permitted on the site due to safety considerations associated with the small area for turning and wind conditions. This generally averted vehicles getting stuck or rolling over on soft ground.
Seasonal scheduling considerations
When scheduling the time for construction activity consideration was given to:
Low water levels associated with late fall to facilitate the placing of aggregate materials. Water levels have been a key factor in establishing project priority concerning implementation, and,
Frost conditions. Frost hardens the ground surface and makes it more suitable for movement of heavy equipment and for trucking materials. On most days the delivery of aggregate materials was made early in the morning. Preferred temperature conditions were below freezing and dry, to minimize the amount of damage to park lawns and asphalt.
Marking the perimeter of the reef
The reef perimeter was marked with temporary caution buoys to facilitate material placement. Reefs were regularly hand sounded to keep reef materials at 1.0 m below datum during construction. Anchored markers (Coast Guard approved) are deployed seasonally to indicate the boundaries of the reef.
Heavy Equipment
Heavy equipment used to build the reef included the use of a 977 CAT frontend loader and a Koehring 6644 backhoe. The Koehring 6644 backhoe was used for placing materials and sculpting the reef while the 977 CAT delivered materials to the backhoe. Onshore roads were required to safely move aggregate to the edge of the boat basin.
Construction
A platform was constructed in the boat basin to extend the backhoe's reach. The platform was constructed with rip rap covered with a surface layer of gabion to slightly above water level. This temporary platform was created by the 977 CAT and was later sculpted by the Koehring 6644 and incorporated into the reef.
A stable pad of gravel (5 cm clear) and gabion (7.5 - 25 cm) was
created upon which the fish reef lies. Quarried rip rap stone
(23 - 60 cm) irregular in shape forms the majority of the reef
and lies halfway across the pad. Small outlying rubble piles resembling
submerged islands have been
created at the outside of the reef. These islands are contained
within the underwater embayments of the reef.
The shoreline has been altered to provide habitat diversity and
now show irregular shoreline features. At the shoreline interface,
rip rap is covered with gabion stone (7.5 - 2.5 cm) and sprays
of gravel (9 mm pea and 5 cm clear). Boulders (23 - 60 cm) have
been placed in areas of
gravel. Armour stone has been placed on the shore to provide platforms
for angling. Filter cloth was been placed between materials of
the reef and soft sediments of the shoreline to provide structural
integrity.
The Ashbridge's Bay fish reef was created in waters with a maximum depth of 3.5 m (relative IGDL datum, 74.005 a.s.l.). The constructed reef covers an area of soft sediments. Aggregate materials were set to a height of up to 2 m above the original bottom substrates. Aggregate material used to complete the fish reef occupies approximately 400 m3.
11. Degree of Environmental Intervention
Morphometry and substrate characteristics were primarily affected. Off-site sediments within the boat basin were not disturbed during construction. No mortality of fish was observed. Construction was in December to minimize environmental impacts and disturbance to the resident fish community.
December construction limited impacts to park use and destruction
of grounds by heavy
equipment travel.
12. Costs
Planning and approvals* $20 000.00
Materials: $15 544.44
Labour (heavy equipment): $ 7 993.44
Monitoring (5 yrs): $ 10 000.00
Total costs: $53 537.88
*While approximately only 2 months worth of actual work time was required for project planning and approval the overall process took approximately 6 months and required daily attention.
13. Biological Assessment
The MTRCA undertakes a Waterfront Monitoring Program across the Metropolitan Toronto waterfront. From this program, baseline monitoring data exists for the Ashbridges Bay boat basin for the following parameters: water quality, sediment quality, benthic invertebrate communities, fisheries communities. Fish community assessment is done in cooperation with OMNR using the SR-20 electrofishing boat. Monitoring of these parameters will continue within the boat basin with special interest being paid to the underwater reef location. Methodologies used for this monitoring program are outlined in, Toronto Waterfront Habitat Rehabilitation Pilot Projects, Technical Report: 1992, available through the MTRCA and 1989 -- 1993 Toronto Waterfront Fish Communities: Summary and Assessment, available through Ministry of Natural Resources, Greater Toronto and Area District.
14. Measures of Success
If diversification of the substrates within Ashbridge's Bay boat basin is successful a corresponding increase in the abundance of fish found within the boat basin and an increase in the number of YOY fish is expected. Ultimately these increases will assist in achieving the Toronto RAP goals of a more diverse and healthy fish community along the Toronto waterfront.
Success Rating: 1 - assessment incomplete
An accurate understanding of the effect of this project on the resident fish community will not be available for five years. Electrofishing has shown an accumulation of fish within the vicinity of the reef, indicating that it may be providing improved habitat.
15. Key References
Danehy, R.J., Reingler, N.H., and Gannon, J.E. 1991. Influence of nearshore structure on growth and diets of yellow perch (Perca flavescens) and white perch (Morone americana) in Mexico Bay, Lake Ontario. J. Great Lakes Res. 17(2):183-193
MTRCA, 1992. Toronto Waterfront Habitat Rehabilitation Pilot Projects. Technical Report: 1992. (Internal publication)
Portt, C.B., and King, S.W. 1991. Fish community structure, abundance, and biomass along three southern Ontario breakwaters and in adjacent reference habitats. Cam Portt and Associates, Waterloo, Ont.
Strus, R., 1994. 1989 - 1993 Toronto Waterfront Fish Communities: Summary and Assessment. Ontario Ministry of Natural Resources, Greater Toronto and Area District.
Correct citation for this contribution:
Vincent, J. 1995. Underwater fish reef creation project within Ashbridge's Bay Park, City of Toronto, p. 121-127. In J.R.M. Kelso and J.H. Hartig [editors]. Methods of modifying habitat to benefit the Great Lakes ecosystem. CISTI (Can. Inst. Sci. Tech. Inf.) Occas. Pap. No. 1.